Majority and minority intrinsic defects in lithium and sodium halides

We present new findings on the enthalpies of formation of vacancies and interstitial ion defects on either sublattice in the alkali halide crystals MX (X=F, Cl, Br and M=Li, Na) using the MPPI model. The model uses a minimum fit to crystal properties and is fully consistent with the dielectric response. The role of the non-Coulombic short range forcesvis-a-vis polarization fields in the stabilization of the defect formation process is examined and discussed in detail. It is shown that it is important to treat the electrostatic polarization caused by the point defect carefully and variation in potential modelling has a comparatively minor effect on the calculations of enthalpies of formation.